Sequential anaerobic/aerobic biodegradation of chlorinated hydrocarbons in activated carbon barriers

Abstract

The aim of this study is to develop a long lasting, sequential anaerobic/aerobic biological activated carbon barrier. In the biobarrier, pollutant adsorption on granular activated carbon (GAC) and biodegradation occur simultaneously. Trichloroethene (TCE), chlorobenzene (CB), and benzene were used as model pollutants. In the first barrier, that was operated under anaerobic conditions with sucrose and ethanol as auxiliary substrates, TCE was completely converted to lower chlorinated metabolites, predominantly cis-dichloroethene (cis-DCE). The reductive dechlorination process was stable for about 300 d, although the concomitant sulphate-reducing and methanogenic processes varied considerably. In the second barrier, that was operated with addition of hydrogen peroxide and nitrate, dechlorination was limited by a lack of oxygen and restricted mainly to CB biodegradation. Additional aerobic batch tests revealed that the metabolites of anaerobic TCE dechlorination, i.e. cis-DCE and vinyl chloride, were oxidatively dechlorinated in the presence of suitable auxiliary substrates such as ethene, CB, benzene, or sucrose and ethanol. During periods of low biological activity, elimination of TCE and CB occurred by adsorption in the GAC barriers. The pre-sorbed pollutants were available for subsequent biodegradation resulting in a bioregeneration of the activated carbon barriers.

Sequential Reductive and Oxidative Biodegradation of Chloroethenes Stimulated in a Coupled Bioelectro-Process

“…12,13 However, the concept of a sequential reductive and oxidative degradation represents an attractive alternative because PCE and TCE are preferably transformed by reductive dechlorination, whereas oxidative degradation for their less chlorinated metabolites, cDCE and VC, has been demonstrated. 14, 15 The implementation of a subsequent oxidative step could overcome the often observed accumulation of less chlorinated metabolites such as VC at contaminated sites, as transformation of cDCE or VC has been shown to be the rate-limiting step in reductive dechlorination. 2 The coupling of electrochemical or electrokinetic processes to biological metabolism offers the possibility to significantly stimulate microbial pollutant degradation.…”

Effects of direct electric current and electrode reactions on vinyl chloride degrading microorganisms

“…VC is known to accumulate at many chloroethene contaminated sites due to incomplete reductive dechlorination of the primary pollutants tetrachloroethene and trichloroethene [3]. Microorganisms capable of aerobic VC degradation have been detected at many contaminated sites but their activity in the field often is limited by a lack of oxygen in the polluted groundwater [20][21][22][23]. Therefore, in situ-generation of oxygen by water electrolysis represents an effective measure to stimulate aerobic bioremediation [7,24].…”

Bio-electro-remediation: electrokinetic transport of nitrate in a flow-through system for enhanced toluene biodegradation

“…Oxygen in the mineral medium was removed by passing through a 30 m silicon tube in dissolved Na 2 SO 3 [26]. In addition, the head space of the model aquifer system was purged with nitrogen every 48 h for 1 h to maintain anaerobic conditions.…”